BIOL 121 Lecture Notes - Allele Frequency, Soapberry, Allopatric Speciation

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6 Apr 2012

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Evolution 6: Sexual Selection
(insert notes from previous day )
Experiment Examples to prove that females do show this choosing behavior
- Long tailed widow bird has a long tail that allows it to be more desirable to the females
therefore experiment was done by changing the tail lengths which resulted in showing those
with the longer tails reproduced more often
* Runaway traits: are far beyond what would be useful for natural selection, however they
continue because the females continue to choose them = reproduction
Examples of runaway traits: plumage of birds, heavy pigmentations to attract females
What about humans? Do we have the same kinds of engraved female selections?
Pheromones are hormones that produce a chemical response in the opposite sex
Experiment: they had males and females from universities
Exp. 1 males had to sleep in a shirt tonight and no added chemicals (no washing or
deodorant) and these shirts were then exposed to females
MHC major histocampability complex a way to measure how genetically close
someone people are
Result: they found the males shirts with different MHC (if they were not on the pill),
those on the pill preferred those with similar MHC
Fertile = want someone very different genetically to have healthy offsprings
Not Fertile = want someone similar so they may raise children, most like you
Exp. 2 same experiment, but this time females slept in shirts
Result: all men found women not on the pill (mid reproductive cycle)
Though it may be subliminal, men are able to sense which women are ready to
reproduce with
- There is some kind of chemical attraction behind our relationships = wanting the
most genetic variation
Summary: characteristics of fundamental asymmetry of sex
Female fitness is limited mostly bt the ability to get resources for producing eggs and rearing
young, while male fitness is limited by the ability to attract females
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